There might be a resource.
Google images search "excavator", "bucket" and "thumb" comes up with a lot of buckets, and you could get some ideas from that.
It looks to me as if that bucket is as open as it will get. And I suspect you'd be better off buying a bucket that does what you'd like rather than trying build new brackets and cylinder attachments.
If that's not feasible, I'd find one that does what you want and copy it.